Overexpression of PAX6(5a) in lens fiber cells results in cataract and upregulation of alpha 5 beta 1 integrin expression

The PAX6 gene, a key regulator of eye development, produces two major prote ins that differ in paired domain structure: PAX6 and PAX6(5a). It is known that an increase in the PAX6(5a) to PAX6 ratio leads to multiple ocular def ects in humans. Here, transgenic mice were created that overexpress human P AX6(5a) in the lens, These mice develop cataracts with abnormalities in fib er cell shape as well as fiber cell/lens capsule and fiber cell/fiber cell interactions. While the structure of the actin cytoskeleton appeared relati vely normal, the cataractous lens expresses increased amounts of paxillin a nd p120(ctn) as well as large aggregates of alpha 5 beta 1 integrin in the dysgenic fiber cells, The elevated amounts of these proteins in the transge nic lens correlated well with elevated levels of their respective mRNAs, To investigate the role of Pax-6(5a) in the upregulation of these genes, a se ries of gel shift experiments using truncated proteins and consensus oligon ucleotides demonstrated the complexity of Pax-6 and Pax-6(5a) binding to DN A, aiding our identification of potential binding sites in the human alpha 5- and beta 1-integrin promoters. Consequent gel shift analysis demonstrate d that these putative regulatory sequences bind Pax-6 and/or Pax-6(5a) in l ens nuclear extracts, suggesting that the human alpha 5 and beta 1 integrin promoters contain PAX6/PAX6(5a) binding sites and maybe directly regulated by this transcription factor in the transgenic lens, We conclude that thes e transgenic mice are good models to study a type of human cataract and for identifying batteries of genes that are directly or indirectly regulated b y both forms of Pax-6.